package com.dmzapp.cashoffer.util;

import java.io.FileInputStream;
import java.io.InputStream;
import java.security.MessageDigest;

public class MD5Checksum {

    public static byte[] createChecksum(String filename) throws Exception {
        InputStream fis = new FileInputStream(filename);

        byte[] buffer = new byte[1024];
        MessageDigest complete = MessageDigest.getInstance("MD5");
        int numRead;

        do {
            numRead = fis.read(buffer);
            if (numRead > 0) {
                complete.update(buffer, 0, numRead);
            }
        } while (numRead != -1);

        fis.close();
        return complete.digest();
    }

    public static String getChecksum4String(String str) throws Exception {
        MessageDigest complete = MessageDigest.getInstance("MD5");
        byte [] b = complete.digest(str.getBytes());
        String result = "";

        for (int i = 0; i < b.length; i++) {
            result += Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1);
        }
        return result;
    }
    
    // see this How-to for a faster way to convert
    // a byte array to a HEX string
    public static String getMD5Checksum(String filename) throws Exception {
        byte[] b = createChecksum(filename);
        String result = "";

        for (int i = 0; i < b.length; i++) {
            result += Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1);
        }
        return result;
    }

    public static void main(String args[]) {
        try {
            System.out.println(getMD5Checksum("apache-tomcat-5.5.17.exe"));
            // output :
            // 0bb2827c5eacf570b6064e24e0e6653b
            // ref :
            // http://www.apache.org/dist/
            // tomcat/tomcat-5/v5.5.17/bin
            // /apache-tomcat-5.5.17.exe.MD5
            // 0bb2827c5eacf570b6064e24e0e6653b *apache-tomcat-5.5.17.exe
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
